I have an on-going discussion with Kucoin, a cryptocurrency exchange, on the issue of whether I can remember security questions that I alledgedly have entered into their system such as:

What is my first dog's name?

What is your mother's maiden name?

Etc.

Now, you should never put real information in such fields, but it turns out that if you put in random strings, someone might eventually prompt you for them which is why it's a good idea to write them down — which I didn't.

But here's the thing: they're still considered private information. And so as part of GDPR, I have a right to see this data, or have it removed from their system. Hence, in terms of 2-Factor Auth, using security questions is as weak as being able to reset authentication by e-mail.

QED. But Kucoin still hasn't succumbed to my argument.